. . . My own feeling is the Leicas didn't mature until the IIIf & g and the M series was already in the pipeline evolving fron the IV prototypes made before WWII.

Ian

Leicas from the early 30s had many of the fine features that gradually evolved into the IIIf. The IIIg was an intermediate step between the IIIf and M series. It's main advantage was the screw mount for older lenses. Leica was wise to drop it in favor of the M series which had a greater future. The best features of Leica have always been designs that were perfected before production began, and fine workmanship. I eventually beat my IIIf purchased new in 1953 to death. The M4 bought in 1970 is still going strong, although it shows much use.